| 摘要 |
PURPOSE:To perform coarse control over a number of turn of a disk without providing a motor rotating speed detecting means, etc., by controlling a motor for driving the disk so as to suppress the run length of data within the specific range when said data exceeds a specific range. CONSTITUTION:The minimum value of the run length RL of NRZ or NRZI codes recorded on the disk 1 is denoted as RLMIN and the maximum value as RLMAX. When the rotating speed of the motor 23 exceeds a specific value, the minimum value (RLMIN)' of the RL of data picked up from the disk 1 in terms of reference clock 24 is made smaller than RLMIN. When the rotating speed of the motor 23 is made smaller than the specific value, the maximum value (RLMAX)' of the RL of pickup data in terms of reference clock 24 is made larger than RLMAX. Those are detected by comparators 5 and 6, and 7 and 8, whose outputs are fed back to the motor 23 to control the rotating speed of the motor 23 approximately to the specified value. |
